Posted
by
kdawson
on Monday February 23, 2009 @09:44PM
from the hot-and-the-cold-of-it dept.

KentuckyFC writes "Supernovae in our part of the Milky Way ought to have a significant impact on the atmosphere. In particular, the intense gamma-ray burst would ionize oxygen and nitrogen in the mid to upper atmosphere, increasing the levels of nitrogen oxide there by an order of magnitude or so. Now a team of Japanese researchers has found the first evidence of a supernova's impact on the atmosphere in an ice core taken from Dome Fuji in Antarctica. The team examined ice that was laid down in the 11th century and found three nitrogen oxide spikes, two of which correspond to well known supernovae: one event in 1006 AD and another in 1054 AD, which was the birth of the Crab Nebula (abstract). Both were widely reported by Chinese and Arabic astronomers at the time. The third spike is unexplained, but the team suggests it may have been caused by a supernova visible only from the southern hemisphere or one that was obscured by interstellar dust."

The Crab Nebula is 6,500 light years away from earth (http://en.wikipedia.org/wiki/Crab_Nebula).

This means the birth of the Crab Nebula was in the year 5446 BC. Mankind witnessed it 6,500 years later.

News stories on such phenomena invariably leave out this little fact, i.e., that which is witnessed by man in the sky usually happened thousands of years earlier than when he actually saw it. This makes it confusing for the average reader.

But isn't it more sensible when speaking in a historical tone to refer to a celestial objects birth relative to our time line and not the objects actual birth?

I suppose it would be astute to word it in the tune of, "1054 AD, which was when man observed the Crab Nebula". This isn't accurate either as it may suggest that the Nebula could have existed prior to the observed date.::shrug::

Try: 1054 A.D. which is when man observed the birth of the Crab Nebula

One thing I'm curious about. Does this mean that we admit freely that extra-solar events affect the climate of this planet? Anyone have a slide rule handy and some star charts or galactic weather maps? Can we calculate probable effect on current climate conditions from extra-solar events?

The author concludes that a supernova has to be within 10 parsecs (30 light years) or so to be dangerous to life on Earth. This is because the atmosphere shields us from most dangerous radiations. Astronauts in orbit may be in danger if a supernova is within 1000 parsecs or so.

No stars currently within 20 parsecs will go supernova within the next few million years....

No. Assuming the resesarch is all legit & valid (I don't feel like carefully reading their methods right now), this still isn't relevant to Global Climate Change because this didn't affect climate.

You've got short term weather. Then you've got the average/trend of weather over very long periods of time, which is the climate. A 3 year (eyeballing it from the graph) spike in nitrogen oxide concentrations isn't considered climate. An effect on Earth, yes it appears that way, but not one that yields biological consequences. That burst vanished as quickly as it appeared. This sorta of stuff isn't even close to causing mass extinctions or new selection pressures.

Besides, the CO2 and other greenhouse gas emissions correlating pretty nicely with with the effects we're seeing, I'm not aware of any spikes in the temperature record that we need gamma ray bursts to explain.

I think one important fact here is that scientists can measure the effect on the atmosphere of an event that happened a thousand years ago. Would it be reasonable to assume that they couldn't measure the effects of what's happening right now?

Yes, the sun variations influence climate. But human emission of gases into the atmosphere also influence climate, and scientists have means to determine the amount of influence due to each effect.

Try: 1054 A.D. which is when man observed the birth of the Crab Nebula

One thing I'm curious about. Does this mean that we admit freely that extra-solar events affect the climate of this planet? Anyone have a slide rule handy and some star charts or galactic weather maps? Can we calculate probable effect on current climate conditions from extra-solar events?

There's a good reason to leave that fact out. It doesn't have bearing on the story. And your date is too precise. I don't know if we know it's position and motion well enough to determine how far away the Supernova was to the nearest year.

I beg to differ. Although I agree with you that it isn't important to get across the subject at hand, it is still very important. If this was something posted up on Yahoo!'s front page, then fine, I can understand. The layman doesn't care about these details.

However, this is being posted on an astro physics website. It may be overly detailed but if you're going to be detailed, you need to be correct. This is especially so when your audience is a bunch of scholars, scientists, and enthusiasts that are in th

Glaring error? Frankly, I thinking giving 1054 AD as the birth of the Crab Nebula is the most precise way of pinpointing that event. We could have obtained absolutely no information about the event before that date anyhow.

Given general/special relativity, appealing to some objective background time and saying that the supernova occurred "simultaneous" to events in 5446 BC on Earth is the truly ridiculous claim on a cosmic scale. To another equally valid observer, those two events are not simultaneous, and could be in a different order.

If our understanding of cosmology or general relativity ever fundamentally changed, it's the date of the observation that's going to actually be relevant. If your audience *is* a bunch of scientists, they're going to recognize this...

This is especially so when your audience is a bunch of scholars, scientists, and enthusiasts that are in the know and recognize glaring mistakes like this.

Or, rather, people who are already damn well aware of this fact. If somebody took the time to point this out in an astrophysics journal, I would assume that they were either being paid by the word, or an exceptionally patronizing person.

And as such, wouldn't it make sense that they assume certain knowledge (such as the fact that the impact of events here on Earth will occur on a timeline relative to the distance from the event) without needing to spell it out?

Would you expect a math journal to explain how addition works before using it in a proof?

You seem very confused about reference frames. There's no "fixed" time reference for the universe, so it seems perfectly reasonable to use the one on Earth where all the readers live. Sure it give jerks like you something to complain about, but the rest of us understand exactly.

There's no "fixed" time reference for the universe, so it seems perfectly reasonable to use the one on Earth where all the readers live.

Well, while the special relativity may claim that all inertial reference frames are equal, the general relativity—especially the Big Bang theory—suggests that there *is* one inertial reference frame that is more equal than others: the rest frame of the cosmic microwave background radiation, which could be termed the "inertial reference frame for the universe".

Having said that, yes, we should give the dates for when the events were observed on Earth. The universe may not revolve around earth (ear

Nice argument but.... Observing the CMBR I can deduce I am at the 'center of the universe' (big-bang's ground-zero). Another observer 10 billion light years away would observe the same thing and is therefore also at the 'center of the universe'.

ie: The big-bang only accounts for the observable universe, it does not account the entire Universe unless you assume universe = Universe.

Observing the CMBR I can deduce I am at the 'center of the universe' (big-bang's ground-zero).

I'm not talking about where the origin of your coordinate system is. I'm talking about how fast your coordinate system is moving relative to any other inertial coordinate system (when people talk about inertial reference frame, they are far less interested in the origin of the coordinate system than they are about how fast it is moving relative to something else).

Try getting yourself a picture of CMB. The largest feature in CMB is the anisotropy that comes from Doppler shift, that is, one side of CMB is blu

"Big Bang is important from this point of view only in that it is the source of CMB, which gives a reference frame for comparison from *anywhere* *anytime* in the universe."

Just as you are (incorectly) assuming things about me and what I have or haven't seen and understood, you are also assuming the CMB is a reference frame that is the same for everyone inside it, I think that assumption is wrong. Neither of us has any evidence other than what we observe from our own (vitually identical) reference frame.

If I can add super-luminar expansion to the big-bang to make it fit the observations what's stopping me from saying it could have been lopsided exansion?

Because the theory that describes the expansion [wikipedia.org], including the inflation era [1], specifically assumes a homogeneous, isotropic universe, as verified by CMB [2]. That's what's stopping you from saying that it could have been a lopsided expansion. There is no theory to support it, except by twisting existing observation to fit someone's ill-conceived idea.

Remember the real power of any theory is not in the power of explanation ("God did it" is a perfectly good explanation for a lot of people), it's in the po

"Remember the real power of any theory is not in the power of explanation ("God did it" is a perfectly good explanation for a lot of people), it's in the power of prediction. What I describing is the currently-accepted standard theory of the universe, and it has proven its worth by predicting a few astronomical phenomena before they were actually observed."

Good point about predictions but you are "preaching to the choir" here. I knew of the quantum fluctuations (also backed up by super-computer simulatio

He is technically correct. Even from our reference frame, the supernova was ~7,500 years old. The time of an event doesn't change with it's location, only with the velocity of the observer. For any observer in the galaxy which is stationary wrt the Earth, the time of the supernova is the same. But for an observer on earth moving close to the speed of light, the time of the event is different from ours.

The time of an event is dependent on the moment when the event enters the light cone of the observer. So 1054 AD is the correct time of the supernova wrt Earth. We can infer that the event occurred at some other time in a different frame of reference but that is not directly observable. Just as we cannot know anything about any events that might be occurring on the opposite side of an event horizon.

An event does not come into existence until its sequalae enter the light cone of the observer. Think about it.

We can indeed infer that in another frame of reference, which is to say another universe than the one we inhabit, the event happened at a different time, but we should always remember that this is a fiction. It is sometimes a convenient shorthand to say that we are seeing back into the past when we look at a distant galaxy, but that phrasing uses older assumptions about the Universe that the theor

That is not how time and the speed of light work.
From the reference point of people on earth, we Witnessed it in 1054. It went supernovae ~6,500 years before 1054.
Depending on which reference point you are claiming... your first sentence comes close to something that makes sense... but no matter what reference point you take, the supernovae still happened ~6,500 years earlier than 1054 to someone standing on earth.

> our statement assumes that there is meaning to simultaneity, which is incorrect.

There IS meaning for simultaneity, but only for each individual observer (observer here includes each sub-atomic particle, no ETs needed). There is also a meaning for observers sharing the same frame, i.e., at rest relative to each other.

Thus, it is accurate to say that the supernova that formed the Crab Nebula occurred 6500 years earlier. In terms of the event that matters (the wave front ionizing atmospheric gasses), ho

This means the birth of the Crab Nebula was in the year 5446 BC. Mankind witnessed it 6,500 years later.

AIUI, it's customary in Astronomy to ignore the time it took for the light to reach us and consider that things in the sky happen when we see them happen. Not that they're not aware of it, it's just that it makes things easier to talk about, especially to laymen. In general, people either understand about the time lag and take it for granted, or neither understand nor care.

Uh, relative to any frame of reference nothing travels faster than light in a vacuum. I could see some kind of refraction slowing the light down, but relativistic effects do not slow down light relative to any frame of reference - only matter.

Now, it is entirely possible that from the frame of reference of the cosmic ray particles that travelled from the Crab Nebula to here that the trip took less time than would be predicted by a speed-of-light limit. However, at no point would such a particle observe li

Don't forget to add in the correction for the universe expanding in that time, and any corrections required for the relative motion between us and the nebula and....

Or you could just quit being pedantic and realize that the standard practice of referring to astronomical events happening when we observe them is not only justified by physics but is also the simplest way that makes sense.

This means the birth of the Crab Nebula was in the year 5446 BC. Mankind witnessed it 6,500 years later.

Actually what this means is that those who think the logic in parent post is valid need to bone up on relativity and light cones. Relative to the Earth, and therefore the majority of correspondents on Slashdot, the event happened in 1054 AD. Probably by coincidence, it also happened when the Earth-Moon double planet was at its aphelion. (And yes, the sinusoidal path of the Earth about the Sun due to the Moon's influence is significant when looking for accurate aphelion and perihelion points. Learned that wh

This means the birth of the Crab Nebula was in the year 5446 BC. Mankind witnessed it 6,500 years later.

As it was outside of our lightcone [wikipedia.org] it cannot be said to have happened at that time for earthlings. Only when it enters our lightcone can the event be said to have happened. It's a tough concept, but time is _not_ the universal constant, the speed of light is.

This means the birth of the Crab Nebula was in the year 5446 BC. Mankind witnessed it 6,500 years later.

Since we're being pedantic, I'd like to ask: from who's point of view? Observers who move in relation to each other will not agree on when spatially separated events happened in relation to each other. There is an inertial frame where the birth of Crab Nebula indeed happened between the start and end of the year 1054 AD on some point of Earth's surface as recorded by the local populace.

That entire series is excellent, but having read all of the books in the series that have been published up to this point makes the wait until next fall for a new hard! Be sure to read the other series that starts with Island in the Sea of Time by S.M. Stirling as it ties in with the event in Dies the Fire.

Hmm... "birth of the Crab Nebula" or "death of the Great Crab Civilization"?

On that note, it looks like the data doesn't go back far enough to provide any evidence for the scenario in Clarke's "The Star"

Well they have only gone down a hundred metres or so to get this data. I wouldn't be surprised if they could double that. Calibration may be an issue until other dates are measured for older volcanoes, etc.

Hmm... "birth of the Crab Nebula" or "death of the Great Crab Civilization"?

The progenitor star was (opinions vary) between approximately 9 and 12 solar masses, and of spectral type A, O, or B. Using standard approximations, this gives a lifetime for the star on the main sequence of 20 to 40 million years.

The most-recent 20-to-40 million years of this planet's history has seen mammals evolve into other mammals, bats develop sonar, whales stop paddling around near the shore and move into deep water, and vari

If these really are the supernovae, doesn't this mean that "model B" is right and "model A" is wrong?

The two models look like extrema that bound the dates.

More interestingly, the sharpness of the spikes indicate that the sealing of atmospheric gases in the ice happens very suddenly. If it did not we would expect to see much broader and probably asymmetrical peaks.

This is consistent with, but does not absolutely prove, a rather prompt mechanism for such sealing, rather than the long lagtime process that is sometimes invoked to explain why temperatures always rise tens or hundreds of years before CO2 levels do in ice core data. It would be very peculiar, albeit not impossible, to have a process that sealed the ice tens or hundreds of years after it was laid down as snow, but did so on a timescale of a year or so.

It would be very peculiar, albeit not impossible, to have a process that sealed the ice tens or hundreds of years after it was laid down as snow, but did so on a timescale of a year or so.

Why peculiar? That's exactly what I would expect. As snow gets piled higher, there will come a point when the weight from the accumulated snow is more than the strength of snow crystals can support. At the crystals get crushed, the structure will change from a porous mass of snow crystals to solid ice with some bubbles of

Why would you expect that ice and snow would happen to be in the range of strength/weight/accumulation parameters that would be required for this process to routinely take place due to a single year's accumulation of snow after a few decades or centuries of nothing much happening?

That combination of timescales--nothing much happening for decades or centuries, then closure in a single year--bounds the acceptable parameters from both sides, which means that it

That combination of timescales--nothing much happening for decades or centuries, then closure in a single year--bounds the acceptable parameters from both sides, which means that it would be a little surprising if they just happened to fall into that range. This is pretty much the textbook definition of "peculiar".

Take an old building. Its structure gradually weakens by the effect of time. Suddenly it collapses. Do you find it peculiar that a building that existed for a hundred years falls down in a matter

Plausiblity for the win! That's a nice example. My counter-example would be the kind of old wooden farm building that I see a lot of, that really does slump slowly to the ground in exactly they way you say buildings don't. I used to wonder at these structures when I was growing up: old barns and outbuildings that would be in a state of almost complete collapse for years, but would never actually fall down. They just eased themselves slowly to the ground as their wooden structure d

Debate is good, and everyone is permitted to have there opinion and ideas, more so when there is perhaps new data.

Why should we not discuss them? Being denied to speak anything against the consensus is what church and queen have done for centuries to keep everyone inline. It not science when you must agree with consensus or get silenced.

If there had been, I suspect more than a couple wise men would've spotted it and thus there would be historical records. Yet, funny enough, no one's been able to identify such an event. Interesting, that...

This was a central piece of evidence in Charles Hapgood's theory of crustal displacement. That theory has been pretty well debunked, the evidence that works in favor of continental drift works against crustal displacement. Similarly, the ice cores from Antartica are datable both by depth and by debris and gasses trapped inside.

Of the Piri Reis map itself, it has some innaccuracies, and seems to have been cobbled together from other maps, but it does have a level of accuracy concerning the New World that o

You're citing an 1980 article from "Aramco World Magazine" to introduce a bunk story on par with lost-city-of-atlantis myths. It's not even a peer reviewed journal. It's a magazine. You're giving these Piri Reis maps much more credit than they deserve. You say they

closely resemble an ice-free Antarctica

but from what I just read the maps didn't even have a waterway between Antarctica and South America. An ice free antarctica should have a *huge* friggin' waterway there.

If these maps are correct, and there was no ice in the 1500's... how were these ice cores found?

They aren't correct. See above.

We have ice cores that we know go back more than 400,000 years. Give the guys who date these cores some credit. To me this iceless-antarctica idea just looks like a retired old historian/cartographer pushing a crackpot hypothesis. Yes, Antarctica wasn't always covered in ice, but that was millions of years ago.

The hypothesis is that Antarctica was ice free in 1500 and that someone mapped it, but we have 400,000 year old ice and a huge pile of ice overall that couldn't have been dumped in five centuries. So the hypothesis is wrong.

Wikipedia says [wikipedia.org] that the little ice age started in 1250 at the earliest, and 1650 at the latest. If the supernova caused it, there was at least a 200 year lag. If you want another coincidence, the Medieval Warm Period [wikipedia.org] peaked during the time of the supernova.

Oddly, there's a quote in the Little Ice Age article from 200 years before the earliest accepted start date (very near the time of the supernova - did the gamma rays precede the visible light photons?) that supposedly predicts the coming cold. That sound